Condensing heat exchanger formed of norbornene polymer

ABSTRACT

A condensing heat exchanger is formed of norbornene polymer, preferably a norbornene homopolymer or copolymer. A plurality of norbornene polymer pellets are melted and extruded to form a first tube. The tube is then blow molded into a mold. A second extruded tube is also blow molded into a U-shape, and the first tube is positioned in the U-shaped opening to form a cell. The ends of the cells are attached to a holding plate by thermal adhesion or heating and flaring. Norbornene polymer possesses exceptional thermal resistance to the high temperature flue vent gases and has physical and chemical resistance to the acidic condensate formed by the condensing heat exchanger.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to a blow moldedcondensing heat exchanger made of a norbornene polymer having thermal,chemical and physical resistant to the conditions of a condensing heatexchanger.

[0002] Condensing heat exchangers are employed in condensing furnaces toincrease efficiency. The condensing heat exchanger cools the heatingfluid to a temperature below the dew point. As the temperature dropsbelow the dew point, a liquid condensate, water vapor, condenses fromthe heating fluid. As the liquid condensate condenses, heat istransferred from the water vapor to the air to be heated. As more heatis produced, the efficiency of the system is increased.

[0003] Polypropylene films are commonly utilized to make a laminatedcondensing heat exchanger material to prevent corrosion of the heatexchanger by the water vapor liquid condensate. In prior condensing heatexchangers, the film is formed by melted polypropylene pellets which areextruded or cast to form a film. The metal surface of the condensingheat exchanger is then heated. The film is applied to the heatedcondensing heat exchanger, and the heated surface slightly melts thefilm, adhering the film to the condensing heat exchanger. A rollerpasses over the surface of the film to further adhere the film to thecondensing heat exchanger. Alternatively, the film is adhered to themetal with an appropriate adhesive and primer.

[0004] Blow molding and extrusion are known process commonly employed tomake bottles or tubes. Polyester is a polymer which is often utilizedduring blow molding or extrusion. However, polyester does not haveacceptable physical, chemical or thermal resistance to the conditions ofa condensing heat exchanger.

[0005] There are several drawbacks to the polypropylene film of theprior art. For one, the metal can corrode if the film is not continuousor if there are holes in the film. Additionally, it is costly tomanufacture and apply the prior art film to the metal heat exchanger.Therefore, it would be advantageous to form a condensing heat exchangerentirely out of a corrosion resistant material.

[0006] Hence, there is a need in the art for a condensing heat exchangermade of a polymer which is capable for withstanding the conditions of acondensing heat exchanger.

SUMMARY OF THE INVENTION

[0007] The present invention relates to a condensing heat exchanger madeof a norbornene polymer.

[0008] The condensing heat exchanger of the present invention is formedof a norbornene polymer, preferably norbornene homopolymers andcopolymers. In a first embodiment, a plurality of norbornene pellets aremelted and extruded from a die to form a hot inner extruded. The tube ispositioned in a mold which encases the tube and pinches off a first end.Air blown into the tube expands the hot tube into the shape of the mold.Preferably, the interior surface of the mold includes a plurality ofgrooves to increase the surface area for heat transfer. Once cooled, theinner tube is removed from the mold. An outer extruded tube is also blowmolded into a U-shape.

[0009] After blow molding, the inner tube is positioned in an opening ofthe U-shaped outer tube, and the ends are attached to a holding plate tocreate a cell. A flue gas flow passage is formed between the inner andouter tubes which release and exchange heat to air which flows betweencells. If the holding plate is made of norbornene polymer, the tubes arethermally adhered to the holding plate. Alternatively, if the holdingplate is formed of metal, the ends of the tubes are heated and flared tosecure the tubes to the metal holding plate. The holding plates and theattached tubes are then positioned in and secured to the heat exchangertransfer box to form a condensing heat exchanger.

[0010] Alternatively, a cell is blow molded in a single process. Anextruded tube is positioned in a mold having a substantially “w-shaped”outer part and a substantially “u-shaped” inner part and blow molded,expanding the tube into the shape of the mold. The ends of the expandedtube are adhered to a blow-molded norbornene polymer plate or flangewhich surrounds and encloses the expanded tube to form the cell. Theflue gases flow through the expanded serpentine tube and transfer heatto the surrounding air to be heated.

[0011] In a third embodiment, a plurality of tubes of a desired length,diameter and thickness are extruded. The plurality of tubes are stackedand the ends are secured to a holding plate to form a shell and tubeheat exchanger.

[0012] Norbornene polymers possess exceptional physical, chemical andthermal resistance to the high temperature flue vent gases and acidiccondensate formed by the condensing heat exchanger.

[0013] Accordingly, the present invention provides a condensing heatexchanger made of a norbornene polymer.

[0014] These and other features of the present invention will be bestunderstood from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The various features and advantages of the invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawing thataccompany the detailed description can be briefly described as follows:

[0016]FIG. 1 illustrates a schematic diagram of a condensing furnacesystem;

[0017]FIG. 2 illustrates a schematic diagram of a pair of cells of acondensing heat exchanger;

[0018]FIG. 3 illustrates a schematic diagram of an apparatus for meltingnorbornene polymer and extruding a tube;

[0019]FIG. 4 illustrates a cross-sectional view of the extrudednorbornene polymer tube positioned in a mold prior to blow molding toform an inner expanded tube;

[0020]FIG. 5 illustrates a perspective view of the norbornene polymertube in the mold prior to blow molding;

[0021]FIG. 6 illustrates a cross-sectional view of the expandednorbornene polymer tube after blow molding;

[0022]FIG. 7 illustrates a cross-sectional view of an extrudednorbornene polymer tube positioned in a U-shaped mold to form an outerexpanded tube;

[0023]FIG. 8 illustrates a cross-sectional side view of the blow-moldedcondensing heat exchanger showing a first type of attachment of a cellto a holding plate;

[0024]FIG. 9 illustrates a cross-sectional side view of a second type ofattachment of a tube to a metal holding plate;

[0025]FIG. 10 illustrates a shell and tube heat exchanger employingextruded tubes of norbornene polymers; and

[0026]FIG. 11 illustrates an extruded tube positioned in a mold to forma cell of a condensing heat exchanger in a single process; and

[0027]FIG. 12 illustrates the finished cell of FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028]FIG. 1 schematically illustrates a condensing furnace system 20.Air and natural gas enters a burner 22 which burns the air and naturalgas by a flame 24 to produce hot combustion products. The hot combustionproducts pass through a primary heat exchanger 26, which cools the hotcombustion products and extracts heat to the air to be heated. Toincrease the efficiency of the system 20, a condensing heat exchanger 28is used to extract additional heat. As the hot combustion gases passthrough the condensing heat exchanger 28, the condensing heat exchanger28 cools the combustion products to a temperature below the dewpoint ofthe combustion products. Water vapor begins to condense, allowing moreheat to be extracted from the combustion products and increasingefficiency. As the liquid condensate condenses, heat is transferred fromthe water vapor to the air to be heated. An inducer fan 30 provides asource of suction on the condensing heat exchanger 28 and assists inpulling the flow of the combustion products through the system 20. Thecombustion products are expelled from the system 20 through a flue 32.

[0029]FIG. 2 illustrates a pair of cells 29 of the condensing heatexchanger 28. Each cell 29 including a flow passage 34 through which thecombustion products or flue gases flow. The hot flue gases enter theflow passage 34 through an inlet 36. As the hot flue gases flow throughthe flow passage 34, heat is transferred to the air to be heated whichflows in the air passage 31 between the cells 29. The cooled flue gasesthen exit the cell 29 through the outlet 38. Although only two cells 29are illustrated, a plurality of cells are employed in the condensingheat exchanger 28.

[0030] Referring now to FIG. 3, one apparatus 40 for forming thenorbornene polymer condensing heat exchanger 28 is schematicallyillustrated. Preferably, the norbornene polymer is a homopolymer or acopolymer. A plurality of norbornene polymer pellets 42 stored in aheated funnel 44 are dropped into a hollow cylinder 46. The pellets 42are heated in the cylinder 46 to form melted norbornene polymer 48, aheated internal screw 50 stirring the melted nonborene polymer 48 duringmelting. The melted nonborene polymer 48 is extruded from a die 52positioned in an opening 54 in the cylinder 46, forming an extrudednorbornene tube polymer 56A.

[0031] As shown in FIG. 4, in one embodiment, the tube 56A is placed onbottom portion 58 of a mold 60A. A top portion 62 overlays the bottomportion 58, encasing the hot extruded tube 56A in the mold 60A.Preferably, the mold 60A include a plurality of grooves 64 on theinterior surface 66.

[0032] Referring now to FIG. 5, when the tube 56A is positioned in themold 60A, a first end 68 of the tube 56A is pinched closed. A blowingmachine 70 positioned on the second end 72 of the tube 56A blows airinto the internal space 74 of the tube 56A, expanding the tube 56A asshown in FIG. 6 until the outer surface 76 of the expanded tube 56Bcontacts the interior surface 66 of the mold 60A. The expanded tube 56Bforms into the shape of the mold 60A, including a plurality of grooves78 which increase the surface area and heat transfer.

[0033] As shown in FIG. 7, a second extruded tube 80A is blow-moldedinto a mold 60B using the above-described method to form a substantiallyU-shaped expanded tube 80B having an opening 82, shown in FIG. 8. Whenthe cell 29 is assembled, the first expanded tube 56B is positioned inthe opening 82 of the second expanded tube 80B, creating a flow passage34 between the expanded tubes 56B and 80B for the passage of flue gases.The end 72 of the first expanded tube 56B and ends 84 of the secondexpanded tube 80B are each attached to an aperture 88 in a holding plateor flange 86 which surrounds the tubes 56B and 80B to form the cell 29.

[0034] If the holding plate 86 is formed of a norbornene polymer, theends 72 and 84 of the expanded tubes 56B and 80B are thermally adheredto the holding plate 86. Although only one cell 29 is illustrated inFIG. 8, a plurality of cells 29 are attached to the holding plate 86,and an air flow passages 31 defined between each of the cells 29. Theholding plate 86 with the attached cells 29 are then positioned in aheat exchanger transfer box 90 of the condensing heat exchanger 28.

[0035] Alternatively, as show in FIG. 9, the holding plate 186 is formedof metal. The ends 72 and 84 of the expanded tubes 56B and 80B areheated and flared to attach each to an aperture 188 of the holding plate186. Although only tube 56B is illustrated, tube 80B is attached in thesame manner.

[0036] Alternatively, as shown in FIG. 11, a cell 229 is blow molded ina single process. An extruded tube 256A is positioned in a mold 258having a substantially “w-shaped” outer part 260A and a substantially“u-shaped” inner part 260B such that a first end 268 of the tube 256A ispinched closed. A blowing machine 270 positioned on the second end 272of the tube 256A blows air into the internal space 274 of the tube 256A,expanding the tube 256B into a serpentine shape being substantially“w-shaped.” The end 268 of the expanded tube 256B is then opened by afinishing operation. The ends 268 and 272 of the expanded tube 256B areadhered to a blow-molded norbornene polymer plate or flange 286 whichsurrounds and encloses the expanded tube 256B, forming the cell 229. Theflue gases flow through the flow passage 234 in the expanded serpentinetube 256B and transfer heat to the surrounding air to be heated.

[0037] Alternatively, an extruded norbornene polymer tube 156 isemployed in a shell and tube heat exchanger 128, as illustrated in FIG.10. Flue gases flow through the plurality of tubes 156 and exchange heatwith air flowing in a shell portion 160.

[0038] Although this invention has been disclosed as being used with acondensing heat exchanger, the present invention can also be utilized ina hot water heater, or other heat exchanger. Additionally, other moldingprocess can be utilized.

[0039] There are several advantages to employing the norbornene polymercondensing heat exchanger 28 of the present invention. For one,norbornene polymer possesses exceptional temperature resistance to thehigh temperature flue vent gases, and has physical and chemicalresistance to the acidic condensate formed by the condensing heatexchanger 28, reducing corrosion. Additionally, the norbornene polymercondensing heat exchanger 28 is inexpensive. Finally, the extruded tubes56B, 80B and 156 can be formed using current commercial extrusion andblow molding processes.

[0040] Accordingly, the present invention provides a condensing heatexchanger made of norbornene polymer.

[0041] The foregoing description is only exemplary of the principles ofthe invention. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, so that oneof ordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specially described. For that reasonthe following claims should be studied to determine the true scope andcontent of this invention.

What is claimed is:
 1. A method for making a heat transfer componentcomprising the steps of: forming a plurality of cells of a norbornenepolymer; and using said cells as part of said heat transfer component.2. The method as recited in claim 1 wherein the step of forming each ofsaid plurality of cells includes melting said norbornene polymer and hotextruding at least one extruded tube.
 3. The method as recited in claim2 wherein the step of forming each of said plurality of cells includesextruding an inner extruded tube and an outer extruded tube, the methodfurther comprising expanding said inner extruded tube with air in aninner mold to form an inner expanded tube and expanding said outerextruded tube with air in an outer mold to form a substantially u-shapedouter expanded tube.
 4. The method as recited in claim 3 wherein saidinner expanded tube and said outer expanded tube include a plurality oftubes grooves formed by expanding said inner extruded tube and saidouter extruded tubes into said inner mold and said outer mold,respectively, each including a plurality of mold grooves.
 5. The methodas recited in claim 3 further comprising the step of attaching an innerend of said inner expanded tube and a pair of outer ends of said outerexpanded tube to a flange to form one of said cells, said inner expandedtube being positioned in an opening of said outer expanded tubepositioned between said pair of outer ends, a flue gas passagecontaining a flue gas being defined between said inner expanded tube andsaid outer expanded tube.
 6. The method as recited in claim 5 whereinsaid flange is made of said norbornene polymer, and the step ofattaching said inner end and said outer ends to said flange includesthermally adhering said inner end and said outer ends to said flange. 7.The method as recited in claim 5 wherein said flange is made of metal,and the step of attaching said inner end and said outer ends to saidflange includes heating and flaring said inner end and said outer ends.8. The method as recited in claim 2 wherein the step of forming each ofsaid plurality of cells include expanding said at least one extrudedtube with air in a mold to form a substantially w-shaped expanded tubeand attaching a pair of ends of said expanded tube to a flange to formone of said cells, a flue gas passage being defined in said expandedtube.
 9. The method as recited in claim 2 wherein said at least oneextruded tube is employed in a shell and tube heat exchanger.
 10. Amethod for making a heat transfer component comprising the step of:melting a norbornene polymer; hot extruding an inner extruded tube andan outer extruded tube; expanding said inner extruded tube with airwithin an inner mold having a plurality of mold grooves to form an innerexpanded tube having a plurality of tube grooves and expanding saidouter extruded tube with air within an outer mold having said pluralityof mold grooves to form a substantially u-shaped outer expanded tubehaving said plurality of tube grooves; attaching an inner end of saidinner expanded tube and a pair of outer ends of said outer expanded tubeto a flange to form one of at least one cell, said inner expanded tubebeing positioned in an opening of said outer expanded tube positionedbetween said pair of outer ends, a flue gas passage containing a fluegas being defined between said inner expanded outer tube and saidexpanded tube; and attaching said at least one cell to said flange, anair flow passage being defined between each of said at least one cell toexchange heat with flue gas flowing through said flue gas passage. 11.The method as recited in claim 10 wherein said flange is made of saidnorbornene polymer, and the step of attaching said inner end and saidouter ends to said flange includes thermally adhering said inner end andsaid outer ends to said flange.
 12. The method as recited in claim 10wherein said flange is made of metal, and the step of attaching saidinner end and said outer ends to said flange includes heating andflaring said inner end and said outer ends.
 13. A heat transfercomponent comprising: at least one cell including at least one expandedtube formed of a norbornene polymer; a flue gas passage to contain aflue gas; and an air flow passage located between each of said at leastone cell to exchange heat with flue gas flowing though said flue gaspassage.
 14. The heat transfer component as recited in claim 13 whereinsaid at least one cell includes an outer expanded tube and an innerexpanded tube and said flue gas passage is located between said expandedouter tube and said expanded inner tube to contain said flue gas. 15.The heat transfer component as recited in claim 14 wherein said expandedouter tube is substantially U-shaped and includes an opening and saidexpanded inner tube is positioned within said opening.
 16. The heattransfer component as recited in claim 14 wherein said inner expandedtube and said outer expanded tube include a plurality of groovedsurfaces.
 17. The heat transfer component as recited in claim 14 whereina pair of outer ends of said outer expanded tube and an inner end ofsaid inner expanded tube are attached to a flange.
 18. The heat transfercomponent as recited in claim 17 wherein said flange is made of saidnorbornene polymer, and said inner end and said pair of outer ends arethermally adhered to said flange.
 19. The heat transfer component asrecited in claim 17 wherein said flange is made of metal, and said innerend and said pair of outer ends are heated and flared to attached saidinner end and said outer ends to said flange.
 20. The heat transfercomponent as recited in claim 13 wherein said at least one cell includesan expanded tube which is substantially w-shaped and forms said flue gaspassage.